diff --git a/whereto/app.py b/whereto/app.py
index fef9636..5157c88 100644
--- a/whereto/app.py
+++ b/whereto/app.py
@@ -27,8 +27,11 @@ from whereto import rules
 def process_tests(ruleset, tests):
     """Run the tests against the ruleset and return the results.
 
-    Results are generated as tuples containing the inputs that did not
-    match the expected value. The first element is the test tuple
+    The return value is a tuple containing a list of tuples with the
+    inputs that did not match the expected value, and a set containing
+    the line numbers of the rules that never matched an input test.
+
+    The first element of the mismatched tuples is the test tuple
     (line, input, expected), and the second element is the list of any
     rules that did match the input pattern.
 
@@ -36,17 +39,44 @@ def process_tests(ruleset, tests):
     :type ruleset: RuleSet
 
     """
+    used = set()
+    mismatches = []
     for linenum, input, code, expected in tests:
         matches = list(ruleset.match(input))
         if len(matches) == 1:
             match = matches[0]
             if (code, expected) == match[1:]:
+                used.add(match[0])
                 continue
-        yield ((linenum, input, code, expected), matches)
+        mismatches.append(
+            ((linenum, input, code, expected), matches)
+        )
+    untested = set(ruleset.all_ids) - used
+    return (mismatches, untested)
 
 
 def main():
     arg_parser = argparse.ArgumentParser()
+    group = arg_parser.add_mutually_exclusive_group()
+    group.add_argument(
+        '--ignore-untested',
+        action='store_false',
+        dest='error_untested',
+        default=True,
+        help='ignore untested rules',
+    )
+    group.add_argument(
+        '--error-untested',
+        action='store_true',
+        dest='error_untested',
+        help='error if there are untested rules',
+    )
+    arg_parser.add_argument(
+        '-q', '--quiet',
+        action='store_true',
+        default=False,
+        help='run quietly',
+    )
     arg_parser.add_argument(
         'htaccess_file',
         help='file with rewrite rules',
@@ -69,7 +99,8 @@ def main():
         ]
 
     failures = 0
-    for test, matches in process_tests(ruleset, tests):
+    mismatches, untested = process_tests(ruleset, tests)
+    for test, matches in mismatches:
         failures += 1
         if not matches:
             print('No rule matched test on line {}: {}'.format(
@@ -82,6 +113,15 @@ def main():
             for match in matches:
                 print('  {}'.format(ruleset[match[0]]))
 
+    if untested:
+        if not args.quiet:
+            print('')
+        for linenum in sorted(untested):
+            if not args.quiet:
+                print('Untested rule: {}'.format(ruleset[linenum]))
+            if args.error_untested:
+                failures += 1
+
     if failures:
         print('\n{} failures'.format(failures))
         return 1
diff --git a/whereto/rules.py b/whereto/rules.py
index 9ed3603..7a9ac16 100644
--- a/whereto/rules.py
+++ b/whereto/rules.py
@@ -96,6 +96,10 @@ class RuleSet(object):
     def __iter__(self):
         return iter(self._rules)
 
+    @property
+    def all_ids(self):
+        return list(self._by_num.keys())
+
     def match(self, path):
         for rule in self:
             m = rule.match(path)
diff --git a/whereto/tests/test_app.py b/whereto/tests/test_app.py
index 48920af..cf0bb87 100644
--- a/whereto/tests/test_app.py
+++ b/whereto/tests/test_app.py
@@ -28,11 +28,11 @@ class TestProcessTests(base.TestCase):
         )
 
     def test_one_match(self):
-        actual = list(app.process_tests(
+        actual = app.process_tests(
             self.ruleset,
             [(1, '/path', '301', '/new/path')],
-        ))
-        expected = []
+        )
+        expected = ([], set())
         self.assertEqual(expected, actual)
 
     def test_two_matches(self):
@@ -40,13 +40,14 @@ class TestProcessTests(base.TestCase):
             2,
             'redirect', '301', '/path', '/duplicate/redirect',
         )
-        actual = list(app.process_tests(
+        actual = app.process_tests(
             self.ruleset,
             [(1, '/path', '301', '/new/path')],
-        ))
-        expected = [
-            ((1, '/path', '301', '/new/path'),
-             [(1, '301', '/new/path'),
-              (2, '301', '/duplicate/redirect')])
-        ]
+        )
+        expected = (
+            [((1, '/path', '301', '/new/path'),
+              [(1, '301', '/new/path'),
+               (2, '301', '/duplicate/redirect')])],
+            {1, 2},
+        )
         self.assertEqual(expected, actual)
diff --git a/whereto/tests/test_rules.py b/whereto/tests/test_rules.py
index 1098afb..6c17fce 100644
--- a/whereto/tests/test_rules.py
+++ b/whereto/tests/test_rules.py
@@ -156,6 +156,18 @@ class TestRuleSet(base.TestCase):
         self.assertEqual(1, len(self.ruleset._rules))
         self.assertIsInstance(self.ruleset._rules[0], rules.RedirectMatch)
 
+    def test_all_ids(self):
+        self.ruleset.add(
+            1,
+            'redirect', '301', '/path', '/new/path',
+        )
+        self.assertEqual([1], self.ruleset.all_ids)
+        self.ruleset.add(
+            2,
+            'redirect', '301', '/path', '/other/path',
+        )
+        self.assertEqual([1, 2], self.ruleset.all_ids)
+
     def test_match_one(self):
         self.ruleset.add(
             1,